1. Field of Invention
The present invention relates to a sensing system for measuring the amount of an analyte to be detected in human interstitial fluid, more particularly, to a resonance-type micro-cantilever sensor for measuring the concentration (or the amount) of an analyte to be detected, such as glucose, in the human interstitial fluid, a fluid channel unit used together with the resonance-type micro-cantilever sensor, a method for measuring the concentration (or the amount) of an analyte to be detected, such as glucose, in the human interstitial fluid by using the fluid channel unit and the resonance-type micro-cantilever sensor, and a sensor system for sensing the amount of an analyte to be detected, such as glucose, in the human interstitial fluid.
2. Description of the Related Art
Diabetes is a common and frequently-occurring disease for the middle-aged and elderly people, and the incidence thereof is increasing with improved living standards. In addition, diabetes, cancer, and cardio-cerebrovascular disease are considered by WHO as the three difficult diseases in the world.
According to the estimation by WHO, the total number of the diabetics in the world is about 170 millions (including 30 millions in China) now, and will increase to 300 millions by 2025. Diabetes has already become one of the ten main causes of death in Asia, and more lives are threatened by it than by infectious diseases. Therefore, it is extremely necessary to take measures to prevent and treat diabetes, and accurate measurement of the glucose concentration in the blood is one of the keys thereto.
The measurement of the glucose concentration in the blood is performed mainly by using the following three methods: an invasive detecting method, a minimally invasive detecting method, and a non-invasive detecting method. At present, the measurement is carried out mostly by using the invasive detecting method in which first, blood is sampled from a finger of a patient, then, the glucose concentration in the blood is detected with chemical methods, for instance, by using enzyme electrodes. In the invasive detecting method, however, expendable material is used, and also the patient has to suffer a certain injury which may bring the patient pain and a risk of being infected. Moreover, the most serious disadvantage of the invasive detecting method lies in that the glucose concentration in the blood can not be measured dynamically and thus the change of the glucose concentration can not be reflected in real time, therefore, the glucose concentration obtained by the invasive detecting method is not proper to be used as excellent reference information. Specifically, the measurement obtained by periodically sampling blood from a finger usually can not reveal all hypoglycemia and hyperglycemia, especially nightly hypoglycemia.
Accordingly, a dynamic, continuous and real-time measurement of the glucose concentration in the blood will greatly promote clinical prevention and treatment of diabetes.
Non-invasive detecting techniques under developed for measuring the glucose concentration in the blood mainly comprise a series of optical methods including near infrared spectroscopy, middle infrared spectroscopy, Raman spectroscopy, polarimetry and the like. When the glucose concentration in the blood is measured by using these methods no injury is produced, which represents a development direction. However, the non-invasive detecting techniques are still under preclinical study phase because of the disadvantages thereof such as low measuring accuracy and low reliability.
In view of the above defects and disadvantages of the invasive and non-invasive detecting techniques, much attention has been paid recently to the minimally invasive detecting method in which the glucose concentration in the blood is detected by extracting the human interstitial fluid and then measuring accurately the glucose concentration in the human interstitial fluid. The minimally invasive detecting method is based on an elementary principle that there is high correlation between the glucose concentration in the blood and that in the human interstitial fluid. In the so-called minimally invasive detecting method, first, the tissue fluid is extracted, with a painless and minimal incision, from the skin surface of a patient, then the glucose concentration in the human interstitial fluid is detected with accuracy, finally, the glucose concentration in the blood is predicted precisely according to the correlation between the glucose concentration in the blood and that in the human interstitial fluid. In addition, because methods, such as low-frequency ultrasonic transdermal treatment and reverse ion electro-osmosis, are used, continuously extracting the human interstitial fluid in the skin is obtained. The minimally invasive detecting method is of great practical significance to achieve dynamical and continuous measurement of the glucose concentration in the blood.
However, since there are various chemicals and trace elements in the human interstitial fluid, how to detect the trace glucose in the human interstitial fluid with selectivity and accuracy is the key to the minimally invasive detecting method. Further, because the patient has to carry with a minimally invasive detecting device all the time in order to perform dynamic and real-time measurement on the glucose concentration in the blood, miniaturization of the minimally invasive detecting device is necessary. Concerning the above, a miniaturized sensor for measuring accurately the amount of the trace glucose in the tissue fluid is the core of the minimally invasive detecting method.